1. Technical Field
The present invention relates to a ferroelectric memory device and a method for manufacturing a ferroelectric memory device.
2. Related Art
A ferroelectric memory device (FeRAM) is a nonvolatile memory that is capable of high-speed operation at low voltages, and its memory cell can be composed with one transistor and one capacitor (1T/1C). Accordingly, ferroelectric memory devices can be integrated to the level of integration of DRAMs, and therefore are highly expected as large-capacity nonvolatile memories. A ferroelectric capacitor composing such a ferroelectric memory device has a structure in which a ferroelectric layer is sandwiched between upper and lower electrodes, and a wiring is connected to each of the electrodes for electrically conducting the electrodes to a peripheral circuit. In this connection, an example of related art is described in Japanese laid-open patent application JP-A-11-150240.
When titanium aluminum nitride (TiAlN) is used as the wiring, its resistance would become very high if the TiAlN is fully nitrided. The resistance can be suppressed low if promotion of nitrization is suppressed, but this method may be accompanied by various disadvantages in return for its benefit. For example, (1) its constituent element Al becomes free and readily diffuses in the capacitor; (2) its oxidation resistance property weakens; and (3) the hydrogen barrier capability may not be achieved.